/*

	ifModified-Etag jQuery Plugin - Copyright (C) 2007, Jorrit Jongma (Chainfire)

	Version: 1.0
	Homepage: http://www.jongma.org/webtools/jquery/
	License: Public Domain / MIT (whatever works for you)
	See Also: http://dev.jquery.com/ticket/1292

	From webpage:

	This plugin provides Etag support to jQuery AJAX calls that have ifModified set.

	Note: I don't advise using this plugin with a jQuery 1.2 unless this page states
	otherwise by the time it is released. This functionality may be incorporated into 1.2 itself.

	Documentation: None necessary. Just include the javascript and Etag will be supported alongside
	Last-Modified method of caching.

	Compatibility: 1.1.2*, 1.1.3a, 1.1.3
	* only tested with older version of plugin

*/

jQuery.extend(jQuery, {
	etag: {},

	ajax: function( s ) {
		// TODO introduce global settings, allowing the client to modify them for all requests, not only timeout
		s = jQuery.extend({}, jQuery.ajaxSettings, s);

		// if data available
		if ( s.data ) {
			// convert data if not already a string
			if (s.processData && typeof s.data != "string")
    			s.data = jQuery.param(s.data);
			// append data to url for get requests
			if( s.type.toLowerCase() == "get" ) {
				// "?" + data or "&" + data (in case there are already params)
				s.url += ((s.url.indexOf("?") > -1) ? "&" : "?") + s.data;
				// IE likes to send both get and post data, prevent this
				s.data = null;
			}
		}

		// Watch for a new set of requests
		if ( s.global && ! jQuery.active++ )
			jQuery.event.trigger( "ajaxStart" );

		var requestDone = false;

		// Create the request object; Microsoft failed to properly
		// implement the XMLHttpRequest in IE7, so we use the ActiveXObject when it is available
		var xml = window.ActiveXObject ? new ActiveXObject("Microsoft.XMLHTTP") : new XMLHttpRequest();

		// Open the socket
		xml.open(s.type, s.url, s.async);

		// Set the correct header, if data is being sent
		if ( s.data )
			xml.setRequestHeader("Content-Type", s.contentType);

/* Original code (1.1.3)
		// Set the If-Modified-Since header, if ifModified mode.
		if ( s.ifModified )
			xml.setRequestHeader("If-Modified-Since",
				jQuery.lastModified[s.url] || "Thu, 01 Jan 1970 00:00:00 GMT" );
*/

/* New code - start */
		if ( s.ifModified ) {
			xml.setRequestHeader("If-Modified-Since",
				jQuery.lastModified[s.url] || "Thu, 01 Jan 1970 00:00:00 GMT" );
			xml.setRequestHeader("If-None-Match",
				jQuery.etag[s.url] || "" );
		}
/* New code - end */

		// Set header so the called script knows that it's an XMLHttpRequest
		xml.setRequestHeader("X-Requested-With", "XMLHttpRequest");

		// Allow custom headers/mimetypes
		if( s.beforeSend )
			s.beforeSend(xml);

		if ( s.global )
		    jQuery.event.trigger("ajaxSend", [xml, s]);

		// Wait for a response to come back
		var onreadystatechange = function(isTimeout){
			// The transfer is complete and the data is available, or the request timed out
			if ( xml && (xml.readyState == 4 || isTimeout == "timeout") ) {
				requestDone = true;

				// clear poll interval
				if (ival) {
					clearInterval(ival);
					ival = null;
				}

				var status;
				try {
					status = jQuery.httpSuccess( xml ) && isTimeout != "timeout" ?
						s.ifModified && jQuery.httpNotModified( xml, s.url ) ? "notmodified" : "success" : "error";
					// Make sure that the request was successful or notmodified
					if ( status != "error" ) {
						// Cache Last-Modified header, if ifModified mode.
						var modRes;
						try {
							modRes = xml.getResponseHeader("Last-Modified");
						} catch(e) {} // swallow exception thrown by FF if header is not available

						if ( s.ifModified && modRes )
							jQuery.lastModified[s.url] = modRes;

/* New code - start */
						// Cache Etag header, if ifModified mode.
						var etagRes;
						try {
							etagRes = xml.getResponseHeader("Etag");
						} catch(e) {} // swallow exception thrown by FF if header is not available

						if ( s.ifModified && etagRes )
							jQuery.etag[s.url] = etagRes;
/* New code - end */

						// process the data (runs the xml through httpData regardless of callback)
						var data = jQuery.httpData( xml, s.dataType );

						// If a local callback was specified, fire it and pass it the data
						if ( s.success )
							s.success( data, status );

						// Fire the global callback
						if( s.global )
							jQuery.event.trigger( "ajaxSuccess", [xml, s] );
					} else
						jQuery.handleError(s, xml, status);
				} catch(e) {
					status = "error";
					jQuery.handleError(s, xml, status, e);
				}

				// The request was completed
				if( s.global )
					jQuery.event.trigger( "ajaxComplete", [xml, s] );

				// Handle the global AJAX counter
				if ( s.global && ! --jQuery.active )
					jQuery.event.trigger( "ajaxStop" );

				// Process result
				if ( s.complete )
					s.complete(xml, status);

				// Stop memory leaks
				if(s.async)
					xml = null;
			}
		};

		// don't attach the handler to the request, just poll it instead
		var ival = setInterval(onreadystatechange, 13);

		// Timeout checker
		if ( s.timeout > 0 )
			setTimeout(function(){
				// Check to see if the request is still happening
				if ( xml ) {
					// Cancel the request
					xml.abort();

					if( !requestDone )
						onreadystatechange( "timeout" );
				}
			}, s.timeout);

		// Send the data
		try {
			xml.send(s.data);
		} catch(e) {
			jQuery.handleError(s, xml, null, e);
		}

		// firefox 1.5 doesn't fire statechange for sync requests
		if ( !s.async )
			onreadystatechange();

		// return XMLHttpRequest to allow aborting the request etc.
		return xml;
	}
});